How to create a continuous flow of water?
You will need an Inflow object and an Outflow object.


Setup your domain object. Add a cube that encloses the entire area you want the water to go (don't make it to big though, as the larger it is the more CPU time your bake will require). Then add a fluid modifier in the Physics panel with the type set to Domain
Add the inflow object at the top of the slide and the outflow object at the bottom. Add fluid modifiers with the appropriate types to the objects.
Add an Obstacle type fluid modifier to the slide and anything else you want to collide with the fluid.
Bake